Fence Line From the erosion & sediment control plan

Fence Length m

The whole run, including the ends turned uphill.

Fabric Height above Ground cm

The exposed height the specification sets.

Buried Toe (Trench Depth + Turn) cm

Fabric carried down the trench wall and turned along its floor before backfill.

Trench Width cm

Trench Depth cm

Posts, Roll & Allowance From the specification and the roll label

Post Spacing m

Roll Width cm

Silt fence fabric is sold slit to height; the roll width is the height you can cut.

Roll Length m

Lap at a Roll Join cm

Fabric overlapped or wrapped round a shared post where one roll ends and the next starts.

Cutting & Damage Allowance %

A planning figure, not a measured loss.

Rolls to Order

— rolls

Fabric length with joins and allowance, divided by the roll length, rounded up

Take-Off

Cut Height of Fabric: — cm
Roll Width Left Over (Negative = Too Narrow): — cm
Roll Joins along the Run: — joins
Fabric Length incl. Joins: — m
Fabric Length incl. Allowance: — m
Fabric in the Fence: — m²
Share of Fabric Buried in the Toe: — %
Posts: — posts
Trench to Dig & Backfill: — m³

Every dimension is the specification's or the plan's: the exposed height, the toe, the post spacing and the join detail differ between authorities and between fabric types, so the tool takes them as inputs and has no figure of its own. Fabric in the fence is the fabric length times the cut height; the order is in whole rolls of the roll width you enter, and if the cut height is wider than the roll the result says so with a negative spare. Posts count both ends of one straight run; a run broken into separate lengths needs one more post per extra length. **This is a quantity take-off, not a design: it does not decide where a silt fence belongs or how much drainage area it can serve.**

Silt Fence Take-Off: Fabric, Rolls, Posts & Trench for a Site — free, with the formula and a worked example, at Textile School.